Recycling cellulose-based materials, such as cardboard and paper, works best when the materials are reasonably clean. The process thus works well with office paper, newsprint, and shipping boxes.
A difficulty arises when such materials are contaminated with oil or grease.
Pizza boxes and take-out food containers are particular culprits. Proper recycling of these containers relies in part on proper curbside preparations. In the case of take-out food containers, proper washing with soap and hot water is required to remove grease. Pizza boxes cannot be washed, and must generally have the bottom portion torn off and discarded separately.
Another difficulty arises even with clean containers. Many food containers are coated with a material such as wax or plastic. For example, the traditional “Chinese Take-out Box,” which was once called an “oyster pail,” is a folded waxed or plastic-coated paperboard container with a solid wire handle. The paraffin-based wax or plastic coating on such containers hinders their recyclability.